What is the regex for empty string?

I prefer /^\s+$|^$/gi to match empty and empty spaces. If you use ^\s*$ you don’t need the or case. Also there is no need for g or i modifiers since this matches the whole line and doesn’t involve any characters with case.

What does \b do in JavaScript?

The RegExp \B Metacharacter in JavaScript is used to find a match which is not present at the beginning or end of a word. If a match is found it returns the word else it returns NULL. Example 1: This example matches the word “for” which is not present at the beginning or end of the word. Click it!

What is Epsilon regex?

Base Rule 1: Epsilon is a regular expression that stands for the the empty string.

What is \s in Java regex?

The regular expression \s is a predefined character class. It indicates a single whitespace character. Let’s review the set of whitespace characters: [ \t\n\f\r] The plus sign + is a greedy quantifier, which means one or more times. For example, expression X+ matches one or more X characters.

What is a regex to match only an empty string?

regex match empty string or word, The value I’m trying to match to can either be a word OR it can be empty. I need a regex that will do one of the following: Match the word ‘default’ or empty string; OR. Match any non empty string that is not ‘default’ The non empty string is important because “” is the same as default in my situation.

How to extract a string using regex?

– [-]* – matching zero or more dashes “-” – [0-9]* – matching zero or more numbers – [ a-zA-Z]* – matching zero or more blank spaces or letters

How to check if a line is blank using regex?

Regex Tutorial – Start and End of String or Line Anchors . great www.regular-expressions.info. Using ^ and $ as Start of Line and End of Line Anchors. If you have a string consisting of multiple lines, like first linensecond line (where n indicates a line break), it is often desirable to work with lines, rather than the entire string.

How to allow empty string using regex in Java?

import re